In the process of integrated circuit manufacturing there is need to handle (manually or automatically) small batches of silicon (or other material) wafers which comprise the substrate in and upon which integrated circuits are fabricated. Typically, the industry moves batches of 25 wafers at a time in cassettes or sealed or unsealed storage containers, hereinafter collectively referred to as cassettes, from one process to another as the finished integrated circuits are manufactured. In a similar fashion, the computer disk industry moves the disk substrates in batches using disk cassettes. Herein, wafers is deined to include integrated circuit wafers, disk substrates and other such items suitable for transporting in cassettes.
The inter-process handling in these industries is often done manually, but with the advent of clean conveyor means, such as the present assignee's CLEAN-DRIVE.RTM. conveyor, the afore referenced cassettes can now be automatically moved between each process location. However, a limitation of such use is the need for the cassettes to be loaded onto a pallet that rides on the conveyor system--the cassettes themselves are not suitable for riding directly on the conveyors. The use of pallets entails added costs due to the requirement to return the empty pallets, and the need to clean, maintain and store the pallets. Another limitation of the use of pallets is that the wafers will generally stand in a near vertical direction. The cassettes are constructed with a pocket for each wafer to prevent the wafers from hitting each other. But vibrations and changing the direction of movement inherent in conveyor systems may cause the wafers to bounce in the pockets possibly damaging the wafers.
It is an object of the present invention to provide an integrated wafer or disk cassette or storage box that does not require the use of a pallet by providing a cassette that will ride directly on driven rollers of a conveyor.
It is another object of the present invention to provide a cassette that lessens the possible damage to the wafers by the vibrations involved with moving the cassette via a conveyor.
It is another object of the present invention to provide a cassette that lessens contamination to the wafers.
Yet another object of the present invention is routinely handled at each wafer processing stop.